The present invention relates, in general, to semiconductor packages, and more particularly, to a novel semiconductor package having high breakdown voltage.
In the past, the semiconductor industry has provided many different styles and configurations of semiconductor packages. Packages used for high power dissipation semiconductor devices often have leads extending only from one side of the package. These leads typically are extensions of a leadframe that extends into the package's body. During the process of molding the body around portions of the leadframe, it is often necessary to utilize alignment pins to hold internal portions of the leadframe in place. These alignment pins extend into the molding cavity during molding operations. When the alignment pins are removed, holes are left in the package body thereby exposing portions of the leadframe to the external environment.
After the encapsulation procedure is complete, foreign material such as mold release compounds are cleaned from the exposed leadframe portions, and the holes are filled with an epoxy or silicone material. The cleaning operation increases the package's cost and typically requires the use of environmentally detrimental chemicals.
Due to thermal expansion differences, the epoxy fill material eventually cracks thereby exposing the leadframe to the environment, and reducing the package's breakdown voltage below the desired value of greater than 1500 volts. Although silicones last longer than epoxy, silicones also fail thereby reducing the package's reliability and breakdown voltage.
In addition, the silicon and epoxy materials used during the fill operation have a limited shelf life. Consequently, the material storage time must be closely monitored thereby further increasing the package's cost.
Accordingly, it is desirable to have a semiconductor package that provides a breakdown voltage in excess of 1500 volts, that does not use epoxy or silicone to fill openings in the package's body, and that seals holes with materials having a long shelf life.